Currently, very little quantitative information is available on the rates and patterns of microbial degradation of mixtures of pollutants. Many different types of interactions between these compounds are possible, including cometabolism, inhibition, and neutrality. Knowledge of these interactions and their kinetics is vital, not only for the design of bioreactors that can be used to remediate contaminated water but also for the prediction of the fate of pollutants in the environment, which is critical for the assessment of ecological and human health risks. Furthermore, knowledge about biodegradation must be relevant to real situations; thus, the impact of factors such as pollutant sorption must be taken into account. The long-term objectives of this research effort are to understand microbial degradation of pollutant mixtures in soil, water, and bioreactor environments, and to harness this knowledge in the form of enhanced bioreactor technology. The specific aims ar to: (1) investigate biodegradation substrate interactions an test a new modeling approach to predict mixed pollutant biodegradation rates; (2) evaluate the impact of sorption to humic acid on biodegradation; (3) determine the relationships between microbial population dynamics an the biodegradation of pollutant mixtures; The research design is based on the measurement of biodegradation rates of single pollutants and pollutant pairs, followed by the application of lumped modeling approaches to rapidly extend the size of the mixtures that can be considered. When the basic mixture kinetics have been analyzed, perturbations to the system, in the forms of sorption and predation, will be applied. The major technique to be utilized is measurement of kinetics in batch bioreactor cultivations, but the most novel and potentially powerful method is the use of SSCP-PCR to observe microbial population dynamics.